Really weird for Mario & Sonic as I backuped my original disc (and that the others backup I did are working perfectly, I also checked the size), and as the others posts I read a while ago stated it as non-working.
Maybe you have a NTSC Wii or used a special option ?
Or maybe you have the cios read retry enabled (or another IOS).
Except if the CIOS on the new loader is a new one ? (I kept the one of the first 0.3).
For the versions, tested both personally (1:1 & Decrypted) and both gave me the "Eject disc" screen.